In general, carbonyl compounds exhibit in vivo toxicity due to their high reactivity. Carbonyl reductase is known to detoxify such carbonyl compounds by reducing them [Udo C. T. Oppermann, Toxicology 144 (2000) 71–81]. Carbonyl reductase usually exists as monomers and has diverse substrate specificities to different carbonyl compounds [B. Wermuth, Clin. Biol. Res. 174 (1985) 209–230].
Generally, the methods of reducing the above carbonyl compounds includes those using the microorganisms that have the reducing enzymes or using the reducing enzymes obtained from a chemical synthesis.
Asymmetric reduction of carbonyl compounds by using microorganisms such as yeast is a very useful method to synthesize optically active chemical compounds. The conventional reduction of carbonyl compounds by using microorganisms, however, yield (S)-alcohols preferably to (R)-alcohols. Asymmetric mixture of (2S,3R) and (2R,3R) compounds is produced when α-substituted β-keto esters are reduced. The ratio between the two products depends greatly on the substituting group at the α position. Generally, yeast is known to produce (S)-3-hydroxy compounds by reducing β-keto esters (European patent 0290385), and carbonyl reductases of yeast, known up to date, produce asymmetric mixture of (2S,3R) and (2R,3R) compounds.
Even though it is convenient and economical to carry out the reduction reaction by the above method using microorganisms, it is difficult to obtain compounds that are highly stereospecific to substrates since many oxidases and reductases exist in reality. Chemical synthesis of reductase requires complex production process, time and cost since many steps must be carried out for the reaction. Therefore, there is a demand for easy and economical methods for obtaining the carbonyl reductase that is highly stereospecific to substrates.
To overcome the above problems, the present invention provides highly stereoselective carbonyl reductase that can be purified and synthesized easily by separating an enzyme that reduces carbonyl compounds from a yeast strain, Kluyveromyces marxianus, by identifying the amino-terminal sequence and by purifying the reductase.